Game Development Crash Course
19 lessons and an hour of video get you started fast and free with Corona SDK game dev!
GameDevMarket.net
Great quality (but budget priced) 2D and 3D artwork you can use in your own games.
Super Sprite Bundle
Royalty-free graphics for 2D games - animated characters, tile sets, etc.
App Vault
Biz app developers - these help you create stunning apps in half the time while saving you tons of money you would have otherwise spent hiring designers.
Pathfinding Tutorial
Use Corona SDK and the free Jumper library to do A* pathfinding in your games - over 60 minutes of video + sample code!